An image interpretation map is usually produced by transferring the interpreted information to a base map which has been prepared in advance. The requirements of the base map should be as follows.

(1) Proper map scale to enable appropriate presentation of interpreted information
(2) Geographic coordinate system to establish the geographic reference
(3) Basic map information to be printed in light tones as background which results in enhancement of interpreted information

Normally a topographic map, plan map or orthophotomap is used as a base map.

A topographic map with a scale of 1:50,000, 1:100,000 or 1:250,000 is usually the preferable base map for higher resolution satellite image interpretation.

For oceanographic purposes or marine science, charts with a scale of 1:50,000 to 1:500,000 should be used as the base map.

Orthophotomaps are more easily used by cartographers for the transfer of interpreted information, particularly in the case of forest classification.

The methods of transfer of information to a base map, are as follows.

(1) Tracing
The interpreted image is traced on to a base map by overlaying on a light table.

(2) Optical projection
The interpreted image is projected via a lens and a mirror onto a base map. The optical zoom transferscope or mirror projector is very useful for image interpretation. (see Figure 7.6.1)

(3) Grid system
Grid lines are drawn on both an image and a base map. Then the interpreted information in a grid on the image is transferred to the corresponding grid on the map.

(4) Photogrammetric plotting
Aerial photographs are interpreted into a thematic map using a photogrammetric plotter. (see Figure 7.6.2)

Copyright © 1996 Japan Association of Remote Sensing All rights reserved